If you are an engineering student->If you ever go outside you'll see tall vegetables with hard brown stems and green tops. We call these trees. People cut them down and turn them into paper. Then they write stuff in them and call them books. Doug and W Milliken wrote such a book, called RCVD. I suggest you read it. If you are in an FSAE team there will be many copies floating around.
If you are just generally interested->if you''ve got data from a constant radius test then plot SWA vs latacc. If the plot curves upwards you have understeer, is flat you have neutral steer, and if it curves down you have steady state oversteer. It is unlikely you want that. This is the understeer gradient at the steering wheel, not really much use. If you divide the gradient by the steering ratio you get the vehicle level understeer. This is where you start to see some useful stuff. The deviation of the line from neutral steer shows how much 'extra' slip angle the front axle needs relative to the vehicle. Since you know the weight distribution you can work out how much force is required at each axle for a given latacc. Then look up Bundorf analysis on wiki. I'm ignoring the yaw rate stuff, that's all in the textbooks (Pacejka's book is probably the best academic ref for it). It is very useful to work out the lateral velocity at each axle. Then you can work out the slip angle at each axle. And that gives you the axle cornering stiffness. If you are going to get into this I strongly recommend analysing your data in Octave rather than Excel.
I'm not entirely sure you have enough data to do the whole job, we measure vy directly, routinely.